Regulation of gene expression is controlled at the levels of transcription, processing, transport, and mRNA translation. The primary goals of this Section are to investigate the transcriptional and translational control mechanisms which mediate such controls. Procedures have been developed to divide the process of transcription initiation into distinct stages. This has allowed the extensive purification of stable, active, RNA polymerase II transcription initiation complexes by glycerol gradient centrifugation and gel filtration. Several transcription initiation factors are stabily bound to the binary RNA polymerase II. DNA. Complex. A 60,000 dalton phosphoprotein specific for active transcription initiation at the Adenovirus 2 major late promoter cap site has been identified and is currently being purified and characterized. To understand the function of eIF-2 subunits during ternary complex formation and guanine nucleotide exchange, and the regulation of these activities by phosphorylation/dephosphorylation mechanisms, the genes for the Alpha, Beta, and Gamma subunits of eIF-2 are being sequenced. HPLC procedures for the large scale isolation of eIF-2 subunits have been developed and the amino-terminal sequences of the Alpha and Gamma subunits determined. Oligonucleotide probes based on these sequences are currently being used to screen cDNA and genomic libraries. The Alpha and Beta subunits of eIF-2 have been shown to participate in guanine nucleotide exchange through their interaction with eIF-2B. The effect of ADP-ribosylation of eIF-2 and eIF-2B on this interaction is being evaluated.